Transcript LHCC review 31.08.99 - INFN-BO

CVD diamonds: Recent Developments and Applications
H. Pernegger, CERN
for the CERN RD42 collaboration
 Overview
 Detector principle
 Recent advancements in CVD diamonds and their understanding
Signal collection
Radiation hardness
New CVD diamonds
 Applications in HEP and other fields
Pixel detector for HEP
Beam monitoring & diagnistics
Medical application
H. Pernegger, CERN, IPRD 2004, May 2004
Motivation to use CVD diamonds
 Use at LHC/SLHC (or similar environments)
 Precision tracking at inner layer required
 Must survive the radiation levels typically present at small radia
 Material properties
 Radiation hard (no frequent replacements)
 Fast signal collection time
 Compact + low Z solid state detector
 Room temperature operation
 Basic types of material
 Poly-crystalline CVD diamond (pCVD)
 Single-crystal CVD diamond (scCVD)
H. Pernegger, CERN, IPRD 2004, May 2004
Basic material constants in comparison
 Low dielectric constant- low
capacitance
 High bandgap - low leakage current
 Fast signal collection
H. Pernegger, CERN, IPRD 2004, May 2004
 Mip signal only 50% of Silicon for
same radiation length
 Collection efficiency <100% (pCVD)
Basic Principle of Operation
 “Solid state Ionization
chamber”
 Contacts both sides
 No doping or junction required
 “planar”
 Structured electrodes with
sizes from mm to cm
 Signal
 Typically use integrated
amplifiers for readout
 Collection distance d = mEt
 Measured charge Q = d/t Q0
H. Pernegger, CERN, IPRD 2004, May 2004
Characterization of CVD diamonds
 Measure charge collection distance (through integrating amplifiers)
 pCVD diamond “pumps” : signal increase by a factor 1.5-1.8
 Filling of charge traps
 Contacts: Cr/Au, Ti/W, Ti/Pt/Au
 Use dots -> strip -> pixel on same diamond (contacts can be removed)
 Typically use 1V/mm as operation point
H. Pernegger, CERN, IPRD 2004, May 2004
CVD diamonds
 Growth side pCVD diamonds
wafer grown up to 5 inch
 RD42 in research project with Element Six Ltd to increase charge
collection distance in pCVD diamond material
H. Pernegger, CERN, IPRD 2004, May 2004
Collection distance on recent pCVD diamonds
 Now reach signals of 9800
e- mean charge
 Most probable signal
8000e CCD = 275mm
 Research program worked
 Diamond available in large
sizes
H. Pernegger, CERN, IPRD 2004, May 2004
Irradiation studies: Protons up to 2.2 x 1015 /cm2
 Signal (or SNR) and spatial resolution before and after irradiation
 Signal decrease starts at 2 x 1015 /cm2
 Resolution 11mm (before) to 7.4mm (after)
 Measured on 50mm pitch strip detector
H. Pernegger, CERN, IPRD 2004, May 2004
New type of CVD diamond: CVD Single Crystals
 Motivation: Avoid defects and charge trapping present in pCVD
diamonds
 remove grain boundaries (homogeneous detector)
 Reduce (or eliminate) charge trapping
 Signal distribution in a single crystal CVD diamond
[Isberg et al., Science 297 (2002) 1670]
H. Pernegger, CERN, IPRD 2004, May 2004
Single Crystal CVD diamonds
 HV and pumping characteristics
No pumping
Full signal at 0.2 V/mm
 Current work with single crystals in cooperation with Element Six
 Improve sample “engineering” (reduce variation)
H. Pernegger, CERN, IPRD 2004, May 2004
Single Crystal : Trancient Current Measurements (TCT)
 Measure charge carrier
properties important for signal
formation
a
 electrons and holes separately
 Use a-source (Am 241) to inject
charge
 Injection
 Depth about 14mm compared to
470mm sample thickness
 Use positive or negative drift
voltage to measure material
parameters for electrons or
holes separately
 Amplify ionization current
H. Pernegger, CERN, IPRD 2004, May 2004
Electrons only
Or
Holes only
V
Ionization current in a sample of scCVD diamond
 Extracted parameters
 Transit time
 Velocity
 Pulse shape
 Transit time of charge cloud
 Signal edges mark start and
arrival time of drifting charge
cloud
 Error-function fit to rising and
falling edge
 Total signal charge
H. Pernegger, CERN, IPRD 2004, May 2004
t_c
Preliminary measurement of velocity on a single crystal
 Average drift velocity for
electrons and holes
 Extract m0 and saturation
velocity
 m0 for this sample:
 Electrons: 1714 cm2/Vs
 Holes: 2064 cm2/Vs
 Saturation velocity:
 Electrons: 0.96 107 cm/s
 Holes: 1.41 107 cm/s
H. Pernegger, CERN, IPRD 2004, May 2004
Preliminary carrier lifetime measurements
 Extract carrier lifetimes from measurement of total charge
 Lifetime: >35 ns for electrons and holes -> larger than transit time
 Charge trapping doesn’t seems to limit signal lifetime -> full charge
collection (for typical operation voltages and thickness)
H. Pernegger, CERN, IPRD 2004, May 2004
Applications of CVD diamonds
 In general CVD diamond is used as detector material in several
fields
 HEP and nuclear phyics
 Heavy ion beam diagnostics
 Synchroton radiation monitoring
 Neutron and a detection ….
 (Short) Selection of Applications in this presentation
 Pixel detector developments using CVD diamond detector
 Beam Conditions Monitoring (e.g. at LHC)
 Beam diagnostics for radiotheraphy with proton beams
H. Pernegger, CERN, IPRD 2004, May 2004
Application I:
Pixel Detectors with ATLAS & CMS FE chips
 Use present implementation of radhard FE chips together with
pCVD (later possible scCVD) diamonds
 Bumpbonding yields ≈ 100% now
H. Pernegger, CERN, IPRD 2004, May 2004
Preparation of pixel test assembly
 Test assembly
 Underbump metalization
SiLab/ Bonn
H. Pernegger, CERN, IPRD 2004, May 2004
Example: FE chip with pCVD diamond
 Source & Testbeam results with pCVD diamond mounted to Atlas Pixel
chip
M. Keil / SiLab/ Bonn
 Spatial resolution (pad size =
50x400mm)
H. Pernegger, CERN, IPRD 2004, May 2004
Application II: Beam Conditions Monitoring
 Common Goal: measure interaction rates &
background levels in high radiation environment
 Input to background alarm & beam abort
 “DC current”
 Uses beam induced DC current to
measure dose rate close to IP
 Benefits from very low intrinsic
leakage current of diamond
 Can measure at very high particle
rates
 Simple DC (or slow amplification)
readout
 Examples:
 See talk by M.Bruinsma for BaBar
 Similar in Belle
 Similar method planned for CMS
H. Pernegger, CERN, IPRD 2004, May 2004
 Single particle counting
 Counts single particles
 Benefits from fast diamond signal
 Allows more sophisticated logic
coincidences, timing measurements
 Used at high particle rates up to
 Requires fast electronics (GHz
range) with very low noise
 Examples
 CMS and Atlas Beam conditions
monitor
Beamloss scenario: study for CMS (1)
 E.g. accidental unsynchronized beam abort
 Instantaneous , difficult to protect against
Unsynchronised beam abort: ~1012 protons lost in IP 5 (CMS) in 260ns
(M. Huhtinen, LHC Machine Protection WG, Oct. 2003)
H. Pernegger, CERN, IPRD 2004, May 2004
Beamloss scenario: study for CMS (2)
 E.g. Loss of protons on collimators close to experiments
(“TAS”)
 Worse in dose rate (>up to 1000 x unsynchronized abort if
consecutive bunches are lost)
 Slower (several turns) therefore possible to protect against if
early signs are detected
(dose [Gy])
(M. Huhtinen, LHC Machine Protection WG, Oct. 2003)
H. Pernegger, CERN, IPRD 2004, May 2004
CMS tests with Cern PS fast beam extraction
2 Diamonds
PS beam monitor
A. MacPherson et al. / CMS-BCM
Almost identical diamond response to
PS beam monitor response (pulse
length 40ns)
Diamond signal current is 1-2 A !
H. Pernegger, CERN, IPRD 2004, May 2004
Single pulses from diamond
• Bias on Diamond = +1 V/um
• Readout of signal:
• 16m of cable
• no electronics
• 20dB attenuation on
signal cable (factor 10)
Atlas Beam Conditions Monitoring
 Time-Of-Flight measurement to distinguish collisions from back
ground during normal running
 Located behind pixel disks in pixel support tube
12ns
Time difference
Need to measure single MIPs radiation hard!
… and very fast: rise time <1ns, width <3ns
H. Pernegger, CERN, IPRD 2004, May 2004
Atlas BCM: single-MIP detector with <1ns rise time

Different versions of FE electronics (Fotec/Austria)



500Mhz (40 dB) (2 stages)
1 Ghz (60 dB) (3 stages)
2 pCVD diamond detector back-to-back
w =360 µm, CCD ~ 130 µm
HV Bias 2V/mm


Source tests and test beam
90Sr
source or 5GeV/c pions
(Pb collimator)
Diamond on support
Scintillator
H. Pernegger, CERN, IPRD 2004, May 2004
Preliminary test results
 MIP signal (testbeam & Sr90 source)
 after 16m of cable
 perpendicular to beam, double diamond assembly
 Rise time 900ps, FWHM = 2.1ns
preliminary
SNR = 7.3:1
H. Pernegger, CERN, IPRD 2004, May 2004
Application III: Diamonds in Proton Therapy:
 Austrian medical accelerator facility
 Cancer treatment and non-clinical
research with protons and C-ions
Conventional X-Ray Therapy
H. Pernegger, CERN, IPRD 2004, May 2004
Protons
1 cm
C-Ions
1 cm
Ion-Therapy
Facility Layout
Synchrotron
Preliminary layout
Injector
 Diamonds used for Beam
Diagnostics:
 High-speed Counting of single
particles in extraction line
 Resolve beam time structure
2 Experimental rooms
 Proton & Carbon Beam
 Energy: 60-240 MeV protons and
120-400 MeV/u C-ions
 Intensity: 1x1010 protons (1,6 nA)
and 4x108 C-ions (0,4 nA)
 Beam size: 4x4 mm2 to 10x10 mm2
H. Pernegger, CERN, IPRD 2004, May 2004
4 Treatment rooms
Testbeam results for Proton Beam Diagnostics
 2 diamond with different pad size + scintilator as
“telescopes” tested at Indiana University Cyclotron Facility
 2.5 x 2.5 mm2 (in trigger) CCD = 190 mm, D= 500 mm
 7.5 x 7.5 mm2 (for analog measurements) CCD = 190 mm, D= 500
mm
trigger
H. Pernegger, CERN, IPRD 2004, May 2004
measured
Signal timing properties
 Rise time : 340ps Duration: 1.4ns
 Single shot
H. Pernegger, CERN, IPRD 2004, May 2004
 Average pulse shape
Signal/Noise and energy dependence
200 MeV
104 MeV
55 MeV
Signal energy dependence
SNR
 Measured most probable S/N ranges from 15:1 to 7:1
H. Pernegger, CERN, IPRD 2004, May 2004
Summary
 CVD diamonds as radiation hard detectors
 High quality polycrystalline CVD diamonds (ccd up to 270mm) are readily
available now in large sizes
 Radiation tests showed radiation hardness up to 2 x 1015 p/cm2
 Single crystal CVD diamonds promise to overcome limitations of
polycrystalline CVD diamonds
 Full signal collection already at lower voltages
 Long charge lifetime
 Very little charge trapping and uniform detector (no grain boudaries)
 There are many applications around which benefit from diamond’s intrinsic
properties
 Strip or Pixel detectors for future high luminosity accelerators
 Beam diagnostics and monitoring
H. Pernegger, CERN, IPRD 2004, May 2004
High-bandwidth amplifier for fast signal measurements
 Use current amplifier to measure
induced current
 Bandwidth 2 GHz
 Amplification 11.5
 Rise time 350ps
 Inputimpedance 45 Ohm
 Readout with LeCroy 564A scope
(1GHz 4Gsps)
 Correct in analysis for detector
capacitance (integrating effect)
 Cross calibrated with Sintef 1mm
silicon diode
 m_e = 1520 cm2/Vs
 I = 3.77 eV +/- 15%
H. Pernegger, CERN, IPRD 2004, May 2004
Irradiation studies: Pions up to 2.9 x 1015 /cm2
 Signal (or SNR) and spatial resolution before and after irradiation
Preliminary results
 50% Signal decrease at approx 3 x 1015 /cm2 * (TO BE CONFIRMED)
 Narrower signal distribution after irradiation
 25% Resolution improvement
H. Pernegger, CERN, IPRD 2004, May 2004